Entropy is alright, but Triforce is just too attractive for most people who would build Entropy bar like...Kha'zix.
Kitae's needs to stop being designed around "something ad carries are supposed to buy for dealing with high health bruisers" because it fails at its intended purpose (lol bruisers build MR too, who knew!), and needs to be "something on-hit magic damage builds can specifically buy to increase their damage". Basically remove the AD from the recipe and give it more oomph on its passive or magic pen or something.
EDIT: Adding my 2nd post onto this one so people don't have to go digging through the thread if they're too lazy to. For shame.
Given that I think Kitae's should be repurposed strictly for giving On-hit magic damage builds more options/power, why not have it become an upgrade to Malady? Perhaps slightly increase the AP or attack speed, but focus mainly on improving the proc (damage, MR shred) so that it actually becomes a force multiplier for on-hit items the way IE is for AD builds.